Speaker
Description
The bending energy of the lipid membrane is central to all biological processes involving lipid vesicles, such as endocytosis and exocytosis. Since most biological systems sustain significant concentration gradients, osmotic pressure differences are potentially key players in biological membrane remodeling processes. In a recent paper [Liu et al., J. Phys. Chem. Lett., 13, 498], we demonstrated using single-component giant unilamellar vesicles (GUVs) that the bending energy stored in a GUV can sustain significant external osmotic stresses coming from concentration imbalances between the regions interior and exterior to the vesicle. For sufficient osmotic gradients (>0.15 atm) the vesicles globally deform into a prolate shape, and upon osmotic reversal the collapsed vesicles release the bending energy by forming monodisperse “daughter vesicles” through an endocytosis-like process. The observed deformation is in qualitative accordance with the traditional theoretical picture based on a continuum elasticity description of the membrane. However, the measured osmotic pressure needed for destabilization of the spherical vesicle is about 6 orders of magnitude higher than predicted by theory. In this talk, I will discuss the possible theoretical causes and practical implications of this large discrepancy, and present recent theoretical efforts in describing the effect of thermal vesicle fluctuations on the shape and stability of GUVs. I will also discuss the implications of a coupling between membrane bending and stretching for the stability of small unilamellar vesicles (SUVs) and its implications for “curvature sensing” in biological systems.
